<style>
body {
  font-family: system, -apple-system, '.SFNSText-Regular', 'SF UI Text', 'Lucida Grande', 'Segoe UI', Ubuntu, Cantarell, sans-serif;
  color: #fff;
  background-color: #8aba87;
  text-align: center;
  font-size: 40px;
}

h2 {
  padding: 0;
  margin: 0;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

#close {
  color: white;
  opacity: 0.7;
  position: absolute;
  bottom: 20px;
  left: 50%;
  transform: translateX(-50%);
  font-size: 12px;
  text-decoration: none;
}

</style>

<h2>Hello World!</h2>
<a id="close" href="javascript:window.close()">Close this Window</a>
